The goal of this work is to determine the role of steriod hormones and related serum factors in the induction and growth of estrogen- dependent tumors. This project is being done utilizing cell lines derived from two estrogen-dependent tumors, a kidney tumor of the Syrian hamster, and a pituitary tumor of the Wistar-Furth rat. This laboratory has established permanent cell lines from both tumors and is studying the hormonal control of growth in vitro.